Abstract: An apparatus and method for determining the state of a switch for use in an HVAC system. The apparatus and method are advantageously configured for use within a heating, ventilation and air conditioning (HVAC) system, in which the sensing of the state of safety switches external to a controller is desirable. A current sensor coupled in series between a current source, a safety switch, and a current load, detects the flow of current from the current source and through the switch and load. A status signal, indicative of the flow of current through the current sensor, is generated for sampling by a microprocessor. The presence or absence of current flow through the current sensor provides an indication as to whether the remotely-located switch is in an open or closed state.